AbstractID: 7110 Title: Effect of the Lung Inhomogeneity Correction in Breast Irradiation Using Various
Algorithms
The effect of the dose inhomogeneity correction for radiotherapy treatment of the
intact breast has been studied using Helax-TMS treatment planning system (TPS)
and Monte Carlo (MC) calculations. The TPS calculations are based on the two
available algorithms: a pencil beam (PB) algorithm and a Collapsed cone (CC)
algorithm. We have calculated the dose for a medium size breast patient with CT
scans and tangential isocentric beam arrangements with wedges. Dose
distributions and cumulative dose volume histograms (DVHs) have been obtained
for the above algorithms with and without the inhomogeneity correction using the
intact breast as the planning treatment volume (PTV) and the lung volume. All the
calculations are normalized at the isocenter. There is a close agreement between
the MC and CC calculations for the lung DVH. Both of these algorithms show a
higher volume of the lung receiving lower and intermediate levels of dose than the
PB with and without inhomogeneity corrections. In the region of the highest dose
the CC and MC calculations show a lower volume than the PB algorithm with
inhomogeneity correction. For PTV, The MC calculations show same level of
coverage as CC calculations. However, both MC and CC show a lower level of
coverage than PB calculations with and without inhomogeneity corrections. This
study shows a close agreement between MC and CC calculations for the breast
geometry.